(15) 15 ELA により形成された poly-si 結晶成長様式 - グレイン形状と水素の関係 - Crystal Growth Mode of Poly-Si Prepared by ELA -Relationship between the Grain Morphology and ydrogens- Naoya KAWAMOTO (Dept. of Electrical and Electronic Engineering) Naoto MATSUO (Dept. of Electrical and Electronic Engineering) We investigate the characteristic of the poly-si film prepared by the excimer laser annealing (ELA) of a-si deposited using plasma enhanced chemical vapor deposition (PECVD) method on SiO 2 / SiN / glass substrate (SiN substrate). Compared with the poly-si film prepared by ELA of a-si deposited by low-pressure chemical vapor deposition (LPCVD) on the quartz substrate, the Raman intensity of the poly-si film on the SiN substrate is larger than that on the quartz substrate. The stress of the poly-si film on the SiN substrate is smaller than that on the quartz substrate. The average grin size of the poly-si film on the SiN substrate is approximately 70nm, and the disk-shaped grain, which is observed for the poly-si film on the quartz substrate, is not observed. The avarage roughness (Ra) of poly-si surface on the SiN substrate is larger than that on the quartz substrate. These phenomena are due to the difference of the crystal growth mechanims of the poly-si film between on the SiN substrate and on the quartz substrate. We discuss these mechanisms from a viewpoint of the hydrogens included in the film and the origin of them. Key words excimer laser annealing, SiN substrate, poly-si, hydogens, burst, crystal growth mechanism 1. まえがき liquid crystal display, LCD 21 polycrystalline silicon, poly-sithin film transistor, TFT (active matrix LCD, AM-LCD) [1,2] poly-si TFT amorphous silicon, a-si 100 LCD LCD system on panel, SOP exicimer laser annealing, ELA
16 (16) poly-si 75 250mJ/cm 2 ELA poly-si super cooled liquid, SCL [3] a-si poly-si [4] solid phase crystalization, SPC [5] 250 350mJ/cm 2 SPC SCL (disk-shaped grain) [6] ELA ELA poly-si poly-si poly-si 2. 実験方法 a-si (PCVD, plasma chemical vapor deposition) SiN 50nm CVD SiO2 50nm SiO2 (50nm) / SiN (50nm) / SiN PE(plasma enhanced)cvd a-si 100nm Si26 (low-pressure CVD, LPCVD) 400 100nm a-si 450 0 90 SiN poly-si 10 21 cm -3 10 20 cm -3 a-si KrF full width at half maximum, FWM 23ns 8 100 200 400 J/cm 2 5.9 5.9 6.5 6.5mm (Raman spectroscopy) (atomic force microscopy, AFM) (scanning electron microscopy, SEM) SEM poly-si (secco etching) poly-si [7]average roughness, Ra 3. 結果と考察 3.1 poly-si の結晶性 SiN poly-si poly-si ELA a-si SiN 60 SiN poly-si poly-si SiN poly-si poly-si 3.2 Vol.53 No.1 (2002)
(17) 17 SiN poly-si Si 521cm -1 SiN poly-si poly-si poly-si SiN poly-si SiN poly-si SiN poly-si poly-si SiN poly-si 3.2 poly-si の表面形状 a-si 250 J/cm 2, 32 poly-si SEM SEM SPC SCL [6] ELA SPC [8] Raman Intensity (arb. unit) 8 6 4 2 0 Fig.1 Relationship between the Raman peak intensity and shot number Raman Peak Shift (cm -1 ) 520 515 510 Fig.2 Relationship between the Raman peak shift and shot number FWM (cm -1 ) 10 5 0 Fig.3 Relationship between the Raman peak FWM and shot number
18 (18) SiN 400 J/cm 2, 100 poly-si SEM SEM poly-si SiN poly-si poly-si SiN poly-si 70nm Ra SiN poly-si Ra poly-si Ra Ra SiN poly-si SiN SiO2, SiN, Ra 1.29nm,0.69nm, 0.23nm poly-si Ra poly-si 3.3 結晶成長機構と水素の関係 SiN poly-si SiN poly-si poly-si SiN poly-si Disk-shaped shaped grain Fig.4 SEM image of the poly-si surface on the quartz substrate 250 J/cm 2, 32shot Fig.5 SEM image of the poly-si surface on the SIN substrate 400 J/cm 2, 100shot Grain Size (nm) 10 3 10 2 10 1 (Dashed Line = Disk Shaped Grain) Fig.6 Relationship between the average grain size, estimated from the SEM image and the shot number Vol.53 No.1 (2002)
(19) 19 SiN poly-si SiN a-si PECVD a-si a-si a-si Si SiN a-si SiN Si SiN poly-si 90 SiN 90 350 400 J/cm 2 SiN [9] 2 450 90 SiO2 250n Ra (nm) 30 20 10 0 Fig.7 Relationship between the average roughness, Ra and shot number [ 10 10 ] 3 Stress (dyn/cm 2 ) 2 1 SiO2/SiN/glass substrate 250mJ/cm 2 quartz substrate 250mJ/cm 2 0 20 40 60 80 100 Fig.8 Relationship between the stress and shot number a-si SiN Substrate Laser Irradiation -Burst Defect ydrogen Fig.9 Schematic model of the nucleation process for poly-si on the SiN substrate
20 (20) SiN 50nm SiO2 a-si a-si a-si SiN SiO2 a-si SiN poly-si a-si SiN SiN a-si PECVD a-si [10] 4. むすび SiN a-si ELA poly-si a-si ELA poly-si poly-si SiN poly-si poly-si SiN poly-si poly-si SEM SiN poly-si 70nm poly-si SiN poly-si poly-si SiN poly-si Ra poly-si ELA a-si Stress Nucleus quartz substrate Melt-Si Substrate Stress Free Nucleus SiN substrate Fig.10 Schematic model for the induced stress of the poly-si films on the quartz substrate and the SiN substrate Stress (dyn/cm 2 ) 10 10 10 9 10 8 10 7 Stress Non-Dehydrogenation 200mJ/cm 2 Non-Dehydrogenation 250mJ/cm 2 Non-Dehydrogenation 300mJ/cm 2 Non-Dehydrogenation 350mJ/cm 2 Non-Dehydrogenation 400mJ/cm 2 Dehydrogenation 90min 200mJ/cm 2 Dehydrogenation 90min 250mJ/cm 2 Dehydrogenation 90min 300mJ/cm 2 Dehydrogenation 90min 350mJ/cm 2 Dehydrogenation 90min 400mJ/cm 2 0 20 40 60 80 100 Fig.11 Relationship between the induced stress of poly-si film on the SiN substrate and the shot number. a-si or poly-si SiO2 SiN Glass Stress Free 100nm 50nm 50nm Fig.12 Schematic model for the origin of the hydrogen included in the poly-si on the SiN substrate Vol.53 No.1 (2002)
(21) 21 SiN ELA Si poly-si 5. 2 12 [1].amada, The Laser Society of Japan, 26 (1998) 40. [2].amada,.Abe and Y.Miyai, Trans.IEICE., 84 (2001) 65. [3] S.R.Stiffler, P.V.Evans and A.L.Greer, Acta Metall Mater., 40(1992)1617. [4] N.Matsuo,.amada, Y.Aya, T.Nouda and T.Miyoshi, J. Vac. Soc. Jpn,. 42 (1999) 741. [5] N.Matsuo, Y.Aya, T.Kanamori, T.Nouda,.amada and T.Miyoshi, Jpn. J. Appl. Phys., 39(2000) 351. [6] N.Matsuo, T.Nouda, N.Kawamoto, R.Taguchi, Y.Miyai and.amada, Materials Transactions, 42 (2001).(to be published) [7] K.Kitahara, A.Moritani, A.ara and M.Okabe, Jpn. J. Appl. Phys., 38 (1999) L1312 [8] T.Noguchi, S.Usui, D.P.Gosain and Y.Ikeda, Mat. Res. Soc. Symp. Proc. 557 (1999) 213. [9] A.S.Grove, Physics and Technology of Semiconductor Devices, John Wiley and Sons, Inc, (1967). [10] M.Kondo, Y.Toyoshima, A.Matsuda and K.Ikuta, J. Appl. Phys. 80(1996) 6061. ( 平成 14 年 8 月 3 日受理 )